1. Field of the Invention
The present invention relates to a thermoplastic elastomer resin composition and a formed article of the same. More particularly, the present invention relates to a thermoplastic elastomer resin composition comprising a urethane-based thermoplastic elastomer and a formed article of the same.
2. Description of the art
Recently, thermoplastic elastomers, which are soft materials with rubber elasticity, need no vulcanization, and are as moldable and recyclable as thermoplastic resins, have been extensively used into various areas, such as automobile parts, home electric appliances, wire coatings, medical equipment parts, footwear and miscellaneous goods.
As examples of conventional thermoplastic elastomers, a urethane-based thermoplastic elastomer, an olefin-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polyvinyl chloride-based thermoplastic elastomer and the like have been developed and come onto market.
Among these thermoplastic elastomers, a urethane-based thermoplastic elastomer is excellent in scratch resistance, oil resistance, heat resistance, abrasion resistance and the like. However, this elastomer exhibits a hardness (HDA) of approximately 80 or more, so that the softness of this elastomer is limited. Further, in a molten state, the viscosity of this elastomer becomes drastically low. For this reason, this elastomer has a disadvantage in that it is difficult to form this elastomer into a thick article by injection molding or the like.
Conventional methods for modifying a urethane-based thermoplastic elastomer are disclosed in the following documents. Unexamined Japanese Patent Application Laid-Open Specification Nos. 6-65467 and 6-107898 disclose a resin composition obtained by melt-blending a urethane-based thermoplastic elastomer with a styrene block copolymer (and/or a hydrogenation product obtained by hydrogenating the styrene block copolymer). Each of Unexamined Japanese Patent Application Laid-Open Specification Nos. 3-234745, 3-234755, 5-171003 and 7-126474 discloses a resin composition comprising a urethane-based thermoplastic elastomer and a hydrogenated styrene block copolymer having a carboxyl group or derivative thereof. Unexamined Japanese Patent Application Laid-Open Specification No. 2-97554 discloses a resin composition comprising a urethane-based thermoplastic elastomer and a hydrogenated styrene block copolymer having an epoxy group or derivative thereof. However, although these resin compositions exhibit a certain extent of softness, these resin compositions does not have desired balances between permanent compression set and hardness. Further, the compatibility among the components of these resin compositions is unsatisfactory. As a result, these resin compositions have a problem in that the abrasion resistance thereof is low.
It is conceivable that in order to impart a moldability and softness to a urethane-based thermoplastic elastomer, a urethane-based thermoplastic elastomer is mixed with another thermoplastic elastomer. However, the compatibility between the thermoplastic elastomer and the urethane-based thermoplastic elastomer is unsatisfactory. As a result, the resultant resin composition has a problem in that the scratch resistance thereof is extremely lowered.
In view of the above-mentioned problems, it is an object of the present invention to provide a thermoplastic elastomer resin composition comprising a urethane-based thermoplastic elastomer and another thermoplastic elastomer, which is excellent in moldability, oil resistance, scratch resistance and softness.